#define  _CRT_SECURE_NO_WARNINGS  1
#include <stdio.h>
int main()
{
	double a, b, c, d, e;

	scanf("%lf %lf %lf %lf %lf", &a, &b, &c, &d, &e);
	double average;
	average = (a + b + c + d + e) / 5;
	printf("%.2lf", average);

	return 0;
}